1. Field of the Invention
The present invention relates to a substrate for a display panel, and a display panel having the substrate, and specifically relates to a substrate for a liquid crystal display panel which includes layers including patterns on a conductive film and an insulating film, and a liquid crystal display panel having the substrate.
2. Description of the Related Art
A common liquid crystal display panel includes an array substrate and a color filter substrate, and a space therebetween is filled with a liquid crystal. On surfaces of the array substrate and the color filter substrate, layers including patterns on a conductive film and an insulating film are stacked.
FIG. 3 is a schematic plan view showing one example of patterns of lines which are formed on a conventional liquid crystal display panel 9, and the lines for one pixel are shown. An array substrate includes a layer where a pattern of a gate signal line 912 and an auxiliary capacitance line 915 is formed and a layer where a pattern of a source signal line 913 and a drain line 914 is formed, and these layers are stacked via an insulating film (not shown) . By these patterns, thin film transistors and predetermined lines are formed.
In order that the thin film transistor and the predetermined lines may have properties as designed, alignment of the pattern of the gate signal line 912 and the auxiliary capacitance line 915 with the pattern of the source signal line 913 and the drain line 914 is required to be performed with predetermined accuracy in forming the patterns. For this reason, after the pattern of the gate signal line 912 and the auxiliary capacitance line 915 and the pattern of the source signal line 913 and the drain line 914 are formed, alignment accuracy between the patterns is measured. If the measured alignment accuracy is out of a predetermined permissible range, the source signal line 913 and the drain line 914 are re-formed.
The measurement of the alignment accuracy is performed using image recognition. Accordingly, a mark or a line for measurement which is used for image recognition is sometimes formed in the source signal line 913 and the drain line 914. For example, in FIG. 3, a linear section 914a extending in an X-axis direction is formed in the drain line 914. Edges of the linear section 914a and edges of the gate signal line 912 are detected using image recognition, and based on a result of the detection, a positional relationship between the linear section 914a and the gate signal line 912 in a Y-axis direction (e.g., a distance D between a centerline C of the gate signal line 912 and a centerline B of the linear section 914a of the drain line 914) is measured.
As a prior art literature relating to the present invention, Japanese Patent Application Unexamined Publication No. 2003-302654 is cited.
Incidentally, a liquid crystal panel is required to increase an aperture ratio of each pixel in order to increase luminance. Accordingly, as shown in FIG. 3, in a case where structural elements 921a to 921e arranged to control alignment of the liquid crystal are provided on a common substrate, the drain line 914 is sometimes arranged to coincide with one of the structural elements 921a to 921e as exact as possible. However, it is difficult to arrange the linear section 914a extending in the X-axis direction to coincide with the structural elements 921a to 921e, so that some sections of the drain line 914 do not coincide with the structural elements 921a to 921e. As a result, the sections which do not coincide with the structural elements 921a to 921e cause a decrease in an aperture ratio of a pixel.
Therefore, it is preferable to decrease the area of the sections of the drain line 914 which do not coincide with the structural elements 921a to 921e as much as possible in order to increase the aperture ratio. However, the linear section 914a is required to have a certain length such that the edges of the linear section 914a can be detected with predetermined accuracy in image recognition. In addition, the widths of the sections of the drain line 914 which do not coincide with the structural elements 921a to 921e cannot be narrowed because narrowing the widths of the sections of the drain line 914 which do not coincide with the structural elements 921a to 921e decreases a process margin for the drain line 914, which may cause a reduction in yields.